So Dr. John Canto, director of the chest pain center at Lakeland Regional Medical Center, and his team reviewed data on more than 1.1 million heart attack patients to find the answer. Reporting in the Journal of the American Medical Association, the group says that the differences have to do with both gender and age.

When women show up at the hospital after a heart attack, they are less likely to report chest symptoms. While the sharp, consistent chest pains that typically signal heart attack in most men (69%) do also appear in the majority of women (58%), women are more likely than men to suffer no chest discomfort at all: 35% of all the patients in the study reported no chest-related symptoms, and more of them were women (42%) than men (30.7%).

Canto and his colleagues analyzed the data further to find out whether the heart attack differences between men and women were also influenced by age. When they compared the data by age group and gender, they found that women younger than 55 were more likely to have atypical heart attack symptoms than either older women or men of the same age.

That may result in delays in life-saving care at the hospital, which may in turn help explain why younger women were two to three times more likely to die of their heart attack than similarly aged men who experienced chest pains. “That’s a huge finding,” says Canto. “We’re trying to better understand what influences age has when looking at differences in gender presentation and mortality.”

Overall, nearly 15% of women died in the hospital after their heart attack, compared with about 10% of men.

Canto says the findings refine doctors’ still crude understanding of how heart disease differs between men and women. It has been known for years that more women may not experience the classic chest pains that men do during heart attack, but the tendency to pigeonhole men and women into different symptom categories is misguided. Right now, “the message on heart attack symptoms is that one size fits all, which is that one set of heart attack symptoms are the same for men and another are the same for all women,” says Canto. “We are challenging that conventional wisdom and I believe that the message should be tailored to high-risk young women who are at the highest risk of dying if they have a heart attack.”

Typically, women are older than men when they suffer first heart attack; in the study, the age difference was about 7 years (74 versus 67). Before menopause, women may be protected by estrogen, which can counter the formation of plaques in heart arteries, the chief driver of heart attacks in men and in older women.

So the heart attacks that strike younger women, Canto says, may be biologically different from those that occur in older women and younger men. Women under 55 are more prone to clot-based heart attacks, or those triggered by spasm of the heart vessels that can block the flow of blood. That may be because they are more likely to be using oral birth control, which can increase the risk of clot formation.

In younger women, instead of chest pains, the symptoms of heart attack may include more generalized pain in different parts of the body, including the jaw, neck, shoulder, back and even stomach. Recognizing that younger women may be less likely to present with the typical chest pains of a heart attack could help more of these patients to get the treatment they need in a more timely manner, says Canto.

For women who are concerned about being able to spot the signs of a heart attack, Canto says the majority of sufferers do experience chest pains. But women should be aware of their risk factors for heart disease, such as high cholesterol, diabetes, smoking and high blood pressure — and those who are at increased risk should become more familiar with other heart-attack signals, such as persistent pain in parts of the body other than the chest.